Preparation of alkyl-substituted aromatic hydrocarbons



Patented Dec. 9, 1947 k 2,432,381

- UNITED STATES I PATENT OFFICE PREPARATION OF ALKYL-SUBSTITUTED AROMATIC HYDROCARBON S Donald D'. Coffman and John R. Roland, .Wil-

mington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application November 28, 1945 Serial No. 631,470

1'7 Claims. (01. 260-671) This invention relates to novel aromatic com- P ds, and mixtures thereof, containing alkyl substitutents, and tea process for the manufacture of such products. More particularly the present invention is directed to a novel process for the preparation of alkyl-substituted aromatic hydrocarbons, especially long-chain alkyl-substituted toluenes, xylenes, ethylbenzenes, propylbenzenes, butylbenzenes, etc.

Heretofore long-chain alkyl-substituted benzenes have been prepared by methods known'to the art, such as by condensing benzene with chlorinated paraflins through the agency of metal halide-type catalysts. The use of halogen compounds adds materially to the cost of these products. Other compounds which have been employed for the introduction of long-chain alkyl groups into aromatic hydrocarbons, according to the prior art, include long-chain alcohols and long-chain olefins, but the use of these reactants has been limited because of their relatively high cost. I

An object of this invention is to provide novel and useful alkyl-substituted aromatic hydrocarbons. A further object is to provide a direct and economical method for preparing these hydrocarbons. Other objects of the invention appear 2 which the alkyl substltuent is ofless than 6 carbon atoms in chain length.

In carrying out the process of the present invention, it is desirable to operate under superatmospheric pressure. The apparatus requirements, therefore, preferably comprise means for heating and agitating such vessels, and appropriate connectin lines, gages, controlling valves, and the like. Preferably means are also provided for deoxygenating the ethylene. If desired, suitable pumps or injectors may be provided for adding solutions or suspensions of the catalyst or additional aromatic hydrocarbon to the reactor. For continuous types of reactors, which may assume any of various forms, suitable pumps and metering devices are provided.

The reactants employed in practicing this invention comprise ethylene, a short-chain alkylsubstituted aromatic hydrocarbon, and, as catalyst, a compound which contains the group C=N-- and is derived from a ketaldone. The

reactants may be brought into mutual contact in their respective additions to the reaction zone. It is generally inadvisable to permit the catalyst to be subjected to elevated temperatures more hereinafter. than momentarily before entering the reaction This invention comprises the introduction of zo The pr s y e at d batc wise. long-chain alkyl groups into short-chain alkyli s y or semi-continuously. The followsubstituted aromatic hydrocarbons by heating ethylene with a short-chain alkyl-substituted aromatic hydrocarbon, under suitable conditions of temperature and pressure, in the presence of a catalytic quantity of a ketaldone derivative containing the group C= At a temperature of 200 to 300 C. and under a pressure of at least 4.00 atmospheres, the desired reaction proceeds at a very coirvenient rate. The products may be regarded as havingthe structure, H(HC2CH2)nR,

in which the symbols n and R have the significance given above.

By short-chain alkyl-substituted aromatic hydrocarbon is meant aromatic hydrocarbons in ing detailed description illustrates one manner of carrying out the batchwise operation of the process.

A pressure-resistant reaction vessel is charged with a short-chain alkyl-substituted aromatic hydrocarbon and catalyst. This charging operation is preferably carried out after purging the reaction vessel of air with deoxygenated nitrogen or other inert gas. In order to prevent entrance of air, the charging is usuallyconducted under a blanket of inert gas. Alternatively, the reaction charge can be sucked into the closed and evacuated reaction vessel by use of a loading lock. The vessel is then closed, evacuated, placed in a shaker provided with a heater and connected to a reservoir of ethylene. Controlling and recording thermocouples are placed iii-position, the vessel pressured with ethylene and heating and agitation are started. 0n reaching the selected reaction temperature, the reaction begins, usually without the induction period which is commonly observed in polymerization reactions. The course of the reaction may be followed by thepressure drop due to the utilization of ethylene. The pressure may be maintained in the desired range by any of several means such as by addition of ethylene from high pressure storage, by injecting short-chain alkyl-substituted aromatic hydrocarbon, or'by injecting a mixture of ethylene and short-chain alkyl-substituted aromatic hydrocarbon. At the end point of the reaction, which is marked by cessation of pressure drop, the vessel is cooled, bled of excess ethylene, opened and the reaction mixture discharged. The product may be isolated by procedures illustrated in the examples, "or by simple modifications thereof readily apparent to one skilled in the art.

In the following examples, reactions were carried out in a 400 cc. reaction vessel. Parts are by weight unless otherwise stated.

Example 1.-A silver-lined high-pressure reaction vessel is charged with 200 parts f cumene and 0.2 part of benzalazine. The-vessel is evacuated, pressured with ethylene (approximate weight ratio, ethylene:cumene=0.25), and heating-and agitation are started. During a reaction time of 14 hours, throughout which the temperatureis maintained'at 248 to 250 C. and the pr ssure at 850 to 1000 atmospheres, there is a to al observed pressure drop of 1330 atmospheres. The vewel is then cooled, bled of excess ethylene, opened and the contents discharged. The crude reaction mixture is submitted to steam distillation to remove unreacted cumene. By this means there is obtained 69 parts of a soft, buff-colored wax. This ethylene/cumene wax contains 86.22% carbon, 13.57% hydrogen, and has an average molecular weight (determined ebullioscopically) of 889. The infrared absorption spectrum of the wax, compared with the infrared absorption spectra of cumene and of polyethylene, shows that the new product absorbs strongly at wave-lengths characteristic of the aromatic C-H group, name-v ly, at 3.28 microns, 3.25 microns, and 3.29 microns. as well as in .the region above 3.3 microns which is characteristic of aliphatic CH: groups. As estimated from the relative intensitiesof absorption in these characteristic regions, the wax appears to contain approximately 20% as much absorbing aromatic C--H as does cumene, which corresponds to an ethylene/cumene ratio of about 15. It is to be understood, of course, that this figure may be in error by as much as several units, due to the difficulties inherent in the method.

That the ethylene/cumene product is not a physical mixture of cumene and polymerized ethylene can be demonstrated by distillation of the product under low pressure. An ethylene/cumene sample, prepared as above, was evacuated for 16 hours in a steam bath at 20 mm. pressure, to remove traces of cumene left after steam distillation. Theproduct was then distilled in a short path still at 0.01 mm. pressure. A foreshot (1) boiling up to approximately 56 C. was

taken. The next fractions were taken as follows:

(2) 58-154 c. at 0.01 mm. (a) 154-202 c. at 0.01 mm.

' (4) 202-226 C. at 0.01 mm.

Allof these, showed strong infrared absorption bands at 3.23, 3.25, 3.29, respectively as well Similar ethylene/cumene waxes are obtained when the above experiment is repeated using the following catalysts: acetone oxime, benzaldehyde mum required for complete reaction and to main- 4 phenylhydrazone, cyclohexanone semicarbazone, benzalaniline, and isobutyraldehyde anil.

The waxy product obtained as described above is converted to a detergent by sulfonating 19 parts of the wax," dissolved 111 50 parts by volume of carbon tetrachloride, with 3.6 parts of chlorosulfonic acid. The sulfonation is accelerated by strong illumination from a 300 watt, clear Mazda lamp located at a distance of 3 inches from the glass reactor. After 3 hours the reaction mixture is poured onto water-ice mixture containing sufflcient sodium hydroxide to neutralize all acid. The carbon tetrachloride is removed by evaporation on the steam bath and the residue is diluted with water and filtered. The filtrate is concentrated by evaporation to separate the sodium salt ofsulfonated. ethylene/cumene. Aqueous solutions of this sodium sulfonatedo not form a precipitate when treated with aqueous solutions of calcium or magnesium salts. This behavior indicates that the sulfonate group entered the molecule on the aromatic ring. Aqueous solutions of the sodium sulfonate of ethylene/cumene foam strongly, wet sulfur and deterge soiled fabric. The dried sodium sulfonate contains 10.45% sulfur.

The long-chain alkyl-substituted aromatic -hydrocarbon prepared as above described can also be sulfonated by a variety of other means. For example, sulfuric acid, fuming sulfuric acid, sulfuric anhydride, or certain SO: addition products with ethers may be used as sulfonating agent in place of the above-described chlorosulfonic acid. Light-colored sulfonation products can be prepared by sulfonating with relatively dilute acid .fOr extended reaction times. For example, sulfonation by means of a large excess of 92 to 96% sulfuric acid at 40 C. to 50 C. for several hours gives fairly complete reaction with little if any darkening. When fuming sulfuric acid is used it is necessary to restrict the excess to the minitain a relatively low temperature. Fuming acids, containing up to 20% free sulfuric anhydride, may be conveniently employed at temperatures ranging from --20 C. to +10 C. Low temperatures are readily maintained by the use of a low boiling solvent for the ethylene products described and for this purpose it may be found suitable to use sulfur dioxide. In order to force the sulfonation to completion, while yet maintaining low reaction temperatures, it is sometimes desirable to conduct the sulfonation in the presence of such water binding agents as phosphoric anhydride, acetic anhydride, acetyl chloride, or other acid chlorides.

Ezampte 2.A silver-lined high-pressure reaction vessel is charged with 200 parts of toluene and 0.2 part of benzalazine. The vessel is closed, evacuated, and pressured with ethylene, the weight ratio of ethylene:toluene'being about 0.2.

Q During a reaction time 0128.75 hours, throughout which the temperature is maintained at 249 to 251 C. and the pressure at 505 to 600 atmospheres. The vessel is then cooled, bled of excess ethylene, opened and the contents discharged. The product is isolated as in Example 1 and amounts to 23 parts. This is an ethylene/toluene wax having an average molecular weight of 369 (ebullioscopic) A product prepared as described above was distilled in a short-path still at 0.01 mm. pressure.

low in Table I.

'of 895 atmospheres.

Calculated from infrared absorption. The average intensitiesot the 3.23;; and 3.25; bands were taken since 5h; vlgeredless influenced by CH, absorption than was the I T he v alnes above are based on the assumed retention of toluenes flve aromatic CH groups bythe product. The other equall possible configuration wherein the ethylene chain is linied to one of the nuclear carbons will give apparent molecular weights equal to 80% ot the above figures.

These data plus thefact that the infrared absorption spectra show strong general absorption in the region characteristic of aliphatic CH: groups, indicate that ethylene and toluene are chemically combined by the reaction described.

Example 3.- A stainless steel-lined high-pressure reaction vessel is charged with 200 parts of toluene and 0.4 partof acetone oxime. The vessel is evacuated and pressured with ethylene, the weight ratio of ethyleneztoluene being about 0.25. During a reaction time of 14.25 hours, throughout which the temperature is maintained at 247 to 250 C. and the pressure at 690 to 980 atmospheres, there is a total observed pressure drop This reaction mixture,

desired results, there must be a weight excess of the aromatic hydrocarbon over the ethylene despite the apparent requirement for an excess of ethylene as judged by the empirical equation previously given. The weight ratio of reactants is conveniently of the order or 0.25 for batch operation but may be as low as 0.07, while higher ratios, for example, up to 0.9 are suitable. In continuous operation, even lower ratios, for example, as low as 0.02, may be practically employed. Generally the lower the weight ratio of reactants the lower the average molecular weight of the product.

As catalyst for inducing the reaction of this invention there may be used any compound which contains the group C=N- and which is derived from a ketaldone, i. e., a ketone or aldehyde, Specific catalysts useful in the practice of this invention include azines (containing the group C=N-N=C such as benzalazine, heptaldazine and .diphenylketazine; oximes (containing the group C=NOH) suchas d-camphor oxlme,

acetone oxirne, alpha-benzil dioxime, butyraldoxime, alpha-benzoin oxime, dimethylglyoxime;

hydrazones (containing the group C=NN hydrazones of cyclohexanone, cyclopentanone,

' acetophenone, menthone, camphor, and benzoworked up as in Example 1, yields 60 parts of an ethylene/toluene wax having an average molecular weight of 656 (determined ebullioscopically).

Example 4.Exampie 3 is repeated using ethylbenzene in place of toluene. A waxy ethylene/- ethylbenzene reaction product is obtained,

The short chain alkyl-substituted aromatic hydrocarbon which is employed as a reactant in the process of this invention may be any of the short chain monoor polyalkyl aromatic hydrocarbons. Preferably short chain monoalkyl-substituted aromatic hydrocarbons containing from seven to eleven carbon atoms are employed. Specific compounds coming within this preferred group include toluene, ethylbenzene, n-propylbenzene, isopropylbenzene (cumene), the butyland amylbenzenes, and aand J8- methylnaphthalenes.

Polyalkylbenzenes are less preferred and those employed preferably should contain a total of not more than five carbon atoms in the alkyl substituents.

The ethylene used in the practice of this invention may contain small amounts of ethane, propane, nitrogen, hydrogen, carbon dioxide or oxygen. Oxygen in concentrations above 1000 ppm. generally operates to the detriment of the reaction. Consequentlyethylene purified to contain less than 100 ppm, generally less than ppm. and preferably less than 10 ppm. of oxygen is employed. Ethylene may be conveniently purifled by suitable scrubbing, by catalytic removal of the impurities or by distillation.

The initial weight ratio of ethylene to aromatic hydrocarbon hereafter called weight ratio of reactants, should be not greater than 1, if excessive independent polymerization of the ethylene is to be suppressed. To accomplish these phenone; semicarbazones (containing the group C=N-NHCONH2) such as semicarbazones of acetone, methyl ethyl ketone, diethyl ketone, biacetyl, cyclopentanone, cyclohexanone, acetophenone, propiophenone, camphor, and hemephenone, Schifis bases (containing the group C=N-) such as benzalaniline, benzal-p-toluidine, benzal-o-toluidine, benzaldehyde derivatives of 'methylamine, ethylamine, and neptylamine; anils and analogous compounds of other amines, such as acetaldehyde anil, acetone anil,

isobutyraldehyde anil, n-butyraldehyde anil, heptaldehyde anil, etc. These catalysts are generally used in amounts from about 0.001% to 0.5% by weight based on the total reactants. While it is generally not necessary, for attaining extremely high rates of reaction or for other special purposes, even higher amounts of catalysts may be used; for example, amounts ranging up to as'high as 1% or even 5% as an upper limit can be employed. For their best utility in the ractice of this invention, the foregoing catalysts should be highly purified. For example, some of the phenylhydrazones and some of the Schiif's bases are relatively unstable and decompose on exposure to moisture or air. When the catalysts show such sensitivity they should be prepared immediately before use. Some, such as benzalaniline, can be satisfactorily stored in a vacuiun what higher pressures, for example, up to 3,000 atms. or more may be employed and are particularly desirable for high rates of reaction. .When operating in a continuous manner, the time of contact influences the reaction temperature .and the operable range given mustbe extended to about 400 C. particularly for short contact times.

, tions.

In general, increase in reaction temperature makes for a decrease in the average molecular weight of the product while an increase in pressure increases the average molecular weight.

The equipment used in the practice of this in- 'vention should be strong enough to withstand the herein, the process of this invention can be easily 4 carried out in a continuous manner in either tubular or autoclave reactors. Continuous operation offers numerous advantages in control of temperature, high space-time yield and increased flexibility in the reactant concentrations that may be employed.

The products or this invention may be empioyed as lubricants, as additives for lubricating oils and greases, and as raw materials for conversion to a wide variety of useful products. Of particular importance are the sulfonated products which are valuable as detergents in hard water and sea water because of the solubility of their alkaline earth metal salts. Various salts of the sulionated products are also useful in wetting, emulsiflcation and other surface active applica- Nitration and chlorination can also be controlled to give mainly nuclear substitution and these products are useful respectively for reduction to valuable long-chain amines and hydrolysis to bactericidal and bacteriostati phenols.

The present invention involves'the discovery that the C=N compounds disclosed herein are excellent alkylatio'n catalysts. In its broadest aspect the invention therefore contemplates the alkylation of various hydrocarbons (isoparaflins, etc.) and other organic compounds, containing a reactive C-H bond, by means of an olefin in the presence of the said alkylation catalyst.

We claim:

1. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the said alkyl-substituted aromatic hydrocarbon with ethylene in the presence of a catalyst containing the C=N-- grouping, said catalyst being selected from the class consisting of the oximes, hydrazones, azines, semicarbazones, Schifi's bases, and anils of ketaldones.

2. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the said alkyl-substituted aromatic hydrocarbonwith ethylene, the initial weight ratio of ethylene:aromatic hydrocarbon being not greater than 1:1, in the presence of a catalyst containing the C =N grouping, said catalyst being selected from the class consisting of the oximes, hydrazones, azines, semicarbazones, SchiiI's bases, and anils of ketaldones.

3. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting cumene with ethylene, the initial weight ratio of ethylene:'cumene being not greater'than 1:1 in the presence of a catalyst containing the C=N- grouping, said catalyst being selected from the class consisting of the 1 assasai oximes, hydrazonea, azines, 'semicarbazones,

' Schiifs bases, and anils ofketaldones.

4. A process for the alkylation of toluene which comprises reacting toluene with ethylene, the in itial weight ratio of ethyleneztoluene being not greater than 1: 1 in the presence of a catalyst containing the C=NgrouDing. said catalyst being selected from the class consisting of the oximes,

hydrazones, azines, semicarbazones, Schiifs bases. and anils of ketaldones. v 1 5. A process for the alkylation of ethylbenzene which comprises reacting ethylbenzene with ethylene, the initial weight ratio of ethylenezethylbenzene being not greater than 1:1, in the presence of a catalyst containing the C=N grouping, saidcatalyst being selected fromthe class consisting of the oximes, hydrazones, azines, semicarbazones, Schifi's bases. and anils of ketaldones.

6. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the saidalkyl-substituted aromatic hydrocarbon with ethylene in the presence of a catalytic quantity of acetone oxime.

'7. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the said alkyl substituted aromatic hydrocarbon with ethylene in the presence of a catalytic quantity of benzalazine.

8. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the said alkyl-substituted aromatic hydrocarbon with ethylene in the presence of a catalyst containing the C=N- grouping, said catalyst being selected from the class consisting of the oximes, hydrazones, azines, semicarbazones,v Schifl's bases, and. anils of ketaldones, at-a temperature in the range of about 200 to 300 0.. under a pressure in the range of 400 to 1500 atmospheres, whereby a waxy alkyl-substituted aromatic hydrocarbon is formed, and thereafter separating the said waxy aikyl-substituted aromatic hydrocarbon from the resultant mixture.

9. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which C., under a pressure in the range of 400 to 1500 atmospheres, whereby a waxy alkyl-substituted aromatic hydrocarbon is formed, and thereafter separating the said waxy alkyl-substituted aromatic hydrocarbon from the resultant mixture.

. 10. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting cumene with ethylene, the

initial weight ratio of ethylene;cumene being not greater than 1:1, in the presence of a catalyst containing the C=N grouping, said catalyst semicarbazones, I

aeaasai alkyl-substituted aromatic hydrocarbons which comprises reacting toluene with ethylene, the

initial weight ratio of ethyleneztoluene being not 15. A process for the synthesisof a waxy long v chain alkyl-substituted cumene derivative which comprises heating about 200 parts by weight of cumene with about 0.2 part of benzalazine at a temperature of about 248 to 250 C. in a closed vessel containing ethylene under a pressure in the range of 850 to 1000 atmospheres, the weight ratio of ethylenezcumene being about 0.25, whereby a waxy alkyl-substituted cumene is formed, and thereafter separating the said waxy product from the resultant mixture.

comprises reacting ethylbenzene with ethylene.

the initial weight ratio 0f.ethylene:ethylbenzene being not greater than 1:1. in the presence of a catalyst containing the C=N grouping, said catalyst being selected from the class consisting of the oximes, hydrazones, azines, semicarbazones, Schiffs bases, and anils of ketaldones. at a temperature in the range of about 200 to 300 C., under a pressure in the range of 400 to 1500 atmospheres, whereby a waxy alkyl-substituted aromatic hydrocarbon is formed, and thereafter separating the said waxy product from the re sultant mixture.

13. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the said alkyl-substituted aromatic hydrocarbon with ethylene in the presence of a catalytic quantity of acetone oxime, at a temperature in the range of about 200 to 300 0., under a pressure in the range of .400 to 1500 atmospheres, whereby a waxy alkyl-substituted aromatic hydrocarbon is formed, and thereafter separating the said waxy alkyl-substituted aromatic hydrocarbon from the resultant mixture.

14. A process for the alkylation of short chain alkyl-substituted aromatic hydrocarbons which comprises reacting the said alkyl-substituted aromatic hydrocarbon with ethylene in the presence of a catalytic quantity of benzalazine. at a temperature in the range of about 200 to 300 C., under a pressure in the range of 400 to 1500 atmospheres, whereby a waxy alkyl-substituted aromatic hydrocarbon is formed, and thereafter separating the said waxy alkyl-substituted aromatic hydrocarbon from the resultant mixture.

16. A process for the synthesis of a waxy long chain alkyl-substituted toluene derivative which comprises heating about 200 parts by weight of toluene and less than 200 partsby weight of ethylene with about 0.2 part of benzalazine at a temperature of about 200 to 300 C. under a pressure in the range of 400 to 1500 atmospheres, whereby a waxy alkyl-substituted toluene is formed, and thereafter separating the said waxy product from the resultant mixture.

1'7. A waxy product consisting essentially of a ;mixture oi compounds of the formula I-I(CH2CH2) HR, in which R is a monovalent hydrocarbon radical derived from a short-chain alkyl benzene by removal of a single hydrogen atom, n being an integer from '7 to 50, said waxy product having been prepared by reacting a short 1 chain alkyl-substituted aromatic hydrocarbon with ethylene in the presence of a catalyst containing the C=N- grouping, said catalyst being selected from the class consistingof oximes,

hydrazones, 'azines; semicarbazones, Schiff's bases and anils of ketaldones, at a temperature in the range of about 200 to 300 0;, under a pressure in the range of 400 to 1500 atmospheres.

DONALD D. COFFMZAN. JOHN R. ROLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,233,408 Flett Mar. 4, 1941 2,332,321 Korpi Oct. 19, 1943 2,373,303 Frey et al Apr. 10, 1945 mm Ne. 2,432,381.

i Certificate of Correction 1 r v DONALD D COFFMAN ET AL. It is hereby certified that er'rorcppears in the printed specification of the ebove numbered patent re uiring correction as follows: Column 1, line 40, for

gV GHQ R; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Qflice.

Signed end sealed this 17th day of February, A. D. 1948.

THOMAS F.

Assistant Oouuntaaimer of Patents.

* December 9 ,1947. 

